Manufacture of steel



UNITED STATES ROBERT ABBOTT HADFIELD, OF WESTMINSTER, ENGLAND.

MANUFACTURE or STEEL.

Specification of Letters Patent.

Patented July 27,1920.

No Drawing. Application filed August 10, 1917, Serial No. 185,523.Renewed May 27, 1920. Serial To all whom it may concern:

Be it known that 1, Sir ROBERT ABBOTT HAD-FIELD, Baronet, F. R. S.,'asubject of the King of Great Britain and Ireland,residing at the city ofWestminster, England, have invented Improvements'in or Relating to theManufacture of Steel, of which the ganese), which is always expensiveand not always readily obtainable in sufiicient quantities to meetpractical requirements, and at present is only obtainable in relativelysmall quantities and at many times its ordinary normal cost.

The invention also has for object to produce from stock or raw materialthat is not of high quality, that is to say, is not specially low insulfur and phosphorus, steels that in addition to being practically freefrom or low in man anese, shall also be low in or practically ree fromsulfur and other injurious impurities and which shall therefore be ofhigh grade, and which, accordingto the amount of carbon present therein,are specially suitable for various purposes.

' A further object of the invention is to improve, when required, thephysical and mechanical properties of steel produced according 'to theinvention, and particularly of medium carbon steels.

For attaining the foregoing objects, H101? ten iron or steel isdecarburized, de'siliconized and demanganized by the open hearth,Bessemer, electric or like process to the desired extent and theresulting product is deioxidized by a deoxidizing agent consistingwholly or mainly of silicon or aluminium, or silicon and aluminium,additional carbon if needed,'being also added to the molten metal byaddition thereto of a carburizing agent of good quality to obtain'thenecessary percentage of carbon.

- The silicon can be added in any suitable form, conveniently in theform of ferro-silicon, andthe aluminium as such. Additional carbon thatmay be required to increase the desired percentage thereof in theresulting steel, can be added at the same time to the molten metal inany convenient form, as for instance in the form of pig iron of goodquality, as for example white iron, or as free carbon, for example asanthracite, and the whole thoroughly stirred together. The addition ofeither or both, of the deoxidizing agents and also the re-carburizingagent, if

used, may be made to the molten metal while it is in the furnace, theresulting steel being afterward run offinto a casting or other ladle orreceptacle in the ordinary way.

Or the required amount of ferro-silicon, or of aluminium, or of both,and of the recarburizing agent, if required, can be added it may be in aliquid condition, to the molten metal while the latter is being run offfrom the furnace into a casting orother ladle or receptacle. Or the saiddeoxid'rzing and recarburizing agents may be placed, it may be in aliquid condition, in the ladle or receptacle and the molten metal runoff from the furnace on to them.

If desired and when practicable, ferromanganese, may also be added tothemolten metal with the ferro-silicon or aluminium, or both, andre-carburizing agent, if used, but in this case a much less quantitythan has heretofore been be needed. a

In the case of medium carbon steel,'suitable for use in the manufactureof high explosive shells and other articles which do not require to behardened in the ordinary sense of the term, the-carbon may vary betweensay about decimal four five to decimal six of one per cent. I

In the case of high carbon steel, the carbon may vary from say aboutdecimal eight of one per cent. of carbon and upward. For use in lieu ofthe ordinary expensive crucible cast steel for the manufacture .ofcutting tools, instruments and the like, and for other purposes, thehigh carbon steel is made of high grade, the amount of silicon presentin such steel being low but varying it maybe up to say about decimalthree of one per cent.

For the manufacture of a medium carbon steel according to the invention,the charge of iron from which it is to be made, for example steelturnings, scrap and the like, may be treated in an open hearth furnace,or Bessemer converter, and the molten metal usual or necessary, willboth, is or are then added in the required amount to and thoroughlymixed with the molten steel, to effect the required deoxidation thereof,which may be done either before or after the metal has been run off fromthe furnace or converter or during such running off. If required, and ashereinbefore stated, pig iron, or anthracite may be added to and mixedwith the molten metal at or about the same time as the deoxidizingagent, to recarburize it to any desired degree.

Or, in carrying out the invention in an open hearth furnace, or in aBessemer converter, the molten metal may practically be completelydecarburized, desiliconized and demanganized and the ferro-silicon, oraluminium, or both, and the pig iron or other recarburizing agent, addedin the required amounts to effect the necessary deoxidation andrecarburization of the resulting metal to )roduce steel of the requiredquality.

r the roduction of medium carbon steel may be e ected in an electricfurnace.

The following are given as examples of analyses of medium carbon steelsproduced according to the invention that have been found to give goodresults under test, namely: 7

0 Si s ,P Mn (a) .49 .03 .ll .01 .15 (b) .55 21.01 .016 .24 .58 .30 .067.041 .54

The first mentioned steel (a) was produced by treating lyddite steelturnings and lyddite steel scrap in the proportion of about seventeenhundredweight of the former to about three hundredweight of the latter,according to the electric process in an electric furnace, and adding tothe treated metal about one hundred and eight pounds of white iron,three pounds of ferro-manganese and one and a half pounds of aluminium,the aluminium being added to the metal when in the ladle into which itwas poured.

The secondly mentioned steel (6) was produced by treating lyddite steel.turnings and lyddite steel scrap in about the same proportions as forsteel (a) by the electric process and adding about two pounds ofaluminium to the ton of treated metal in the furnace. v

The thirdly mentioned steel (0) was produced by treating a charge of 80%ordinary hematite and 20% scrap in a converter and adding to abouteighty nine decimal seven nine per cent. of the blown metal in theladle, about nine decimal six five per cent. of good quality pig iron,about decimal five six of one per cent. of ferro-manganese and aboutdecimal two per cent. of aluminium.

For producing high grade steel, the charge of iron from which it is tobe made, for example steel turnings, scrap and the like, may be treatedaccording to the open hearth, Bessemer or like processes and afterwardby the electric process, or wholly by the electric process in anelectric furnace, so as to produce molten metal practically free from orvery low in carbon, silicon, sulfur, phosphorus, manganese and otherimpurities, such metal being deoxidized by the addition of silicon, forexample ferro-silicon, alumini- .um, or ferro-silicon and aluminium, and

recarburized by the addition of a carburi'zing agent of good quality, asfor example good quality pig iron, for instance white iron, oranthracite, the deoxidizing agent and recarburizing agent being added'insuch quantities as to leave in the finished steel the required amount ofcarbon, or carbon and silicon, to produce high grade steel of therequired quality. The deoxidizing and recarburizing agents can'be addedto the purified molten metal at any desired stage of the process, thatis to say, while it is in the furnace, or while it is running from thefurnace, or while it is in a ladle or other receptacle into which it hasbeen run, as hereinbefore stated.

The following are examples of analyses of high carbon high grade steelproduced according to the invention that have been found suitable foruse as cutting tools C Si S P Mn (d) .82 .18 .020 .016 .24 (e) .80 .27.010 .020 .06

The'high carbon steel (:21) was produced by treating in an electricfurnace, a change comprising about ninety nine hundredweights of lydditesteel turnings, about twenty six tons of lyddite steel scrap, addingabout eight and one half hundred-weights of good quality pig iron andabout two hundred-wei hts of carburite and adding about six poun ds ofaluminium to the resulting metal when run into a'ladle.

The high carbon steel (6) was produced by treating in an electricfurnace about five tons of lyddite steel turnings and one and a quartertons of lyddite steel scrap and adding to the finished steel when pouredinto a ladle about seven pounds of aluminium.

If desired, another metal as for example, nickel, chromium, aluminium,copper and so on, or two or more of such metals may be added to steelproduced according to this with the sulfidaggregate disconnectedthereinvention to produce special alloys of steel designed for differentpurposes. Thus, an alloy made of high grade steel with nickel andchromium and suitable for use in the manufacture of armor piercingprojectiles, may contain for example about 56% C, 14% Si, 09% Mn, 2.75%Ni and 2.5% Cr, sulfur and phosphorus being very low.

To improve, when required, the physical or mechanical properties ofsteel produced according to the invention and particularly of mediumcarbon steel, that is to say, steels containing about decimal four todecimal six of one per cent. of carbon and designed for the manufactureof high explosive shells and other articles that do not require to behardened in the ordinary sense of the term but which, in addition tobeing capable of being readily forged or pressed to shape, require to bevery stiff and tough and'to give a high degree of elongation under test,say for example from fifteen to thirty per cent. of elongation, the saidsteel is subjected to a suitable heat treatment. This heat treatment canbe varied but may'consist for example in heating the steel to a suitablyhigh temperature, cooling it, as by quenching it in a cooling medium, asfor example water or oil, either to the temperature of the coolingmedium or of the external atmosphere,

or to a temperature above the ordinary atmospheric temperature, as bywithdrawing it from the cooling medium at a suitable stage of thecooling, reheating it to a high temperature but to a less degree thanthe first heating and allowing it to cool either slowly -or quickly,some or the whole of these operations being repeated or not as may befound necessary. Thus the steel may advantageously be heated to about850 0.,

say 855 (3., then quenched in. water and afterward reheated to say about615 C. and

allowed to cool slowly in the air. The steel may be thusheat treatedafter it has been converted by pressing or forging into the desiredarticle for example, a shell.

In steel low in manganese and produced as hereinbefore described, sulfurpresent therein as sulfid of iron is found, as shown byphoto-micrographs of the steel, to exist for the greater part, in thecast metal, in the form of very small globules or specks of sul- 'fidaggre ates distributed. throughoutthe crystals 0 ferrite rather than'assegregated into larger masses located between the crystals of ferritewhich would weaken the cohesion of'the crystals, with the result thatthe sulfur present has no harmful effect on the steel as determined bytests thereof, while, after heat treatment of the steel the sulfurisfound to have a beneficial effect resulting as shown byphoto-micrograph of the steel,

through, being in the form of very. small angular crystals.

As the deoxidizing agents," silicon and aluminium are the chemicalequivalents of each other and as the atomic weight of silicon and ofaluminium is about half the atomic weight of manganese, the elementssilicon and aluminium either singly or together are included in thegeneral term light deoxidizing agent hereinafter used in some of theclaims to distinguish such element or elements from the relatively heavydeoxidizing agent, manganese.

No claim is made broadly to the use of silicon and aluminium asdeoxidizing agents, the use of which for this purpose being known.

What I claim is 1. The manufacture of steel containing from aboutdecimal three of one per cent. to one percent. and upward of carbon andpractically free from or low in manganese consisting in decarburizing,desiliconizing and demanganizing a molten charge of iron to the desireddegree and deoxidizing the resulting product byv a light deoxidizingagent.

.2. The method of producing steel free from or low in managanese andcontaining from about decimal threeof one per cent. to one per cent. andupward of carbon, consisting in decarburizing, desiliconizing anddemanganizing a molten charge of iron to the desired degree anddeoxidizing the resulting molten metal by a light deoxidizing agent andrecarburizing it to the desired degree by'addition thereto of arecorburizing agent.

3. The method of producing steel free from or low in managanese andcontaining from about decimal three of one per cent. to one per cent.and upward of carbon, consisting in completely decarburizing,desiliconizing and demanganizing a 'molten charge of iron, anddeoxidizing the resulting molten metal by addition thereto ofa lightdeoxidizing agent and recarburizing it to the desired degree by additionthereto of a recarburizing agent.

.4. The method of producin steel free from or low in mana anese ancontaining from about decimal t ree of one per cent. to one per cent.and upward of carbon, consisting 1n decarburiz ng, deslhcomzing anddemanganizing a molten charge of. iron to the desired degree by the openhearth method of treatment Sand deoxidizing the resulting metal byaddition thereto of a light deoxidizing agentv and recarburizmg .it tothe desired degree by addition thereto of a recarburizing agent.

5. The method of producing high grade steel from lower gradematerial andcontaining from about decimal three of one per cent. to one per cent.and upward of carbon,

consisting in melting a charge of iron and treating it by the electricfurnace process so as to produce molten metal practically free from orVery low in carbon silicon, sulfur, phosphorus and manganese,deoxidizing the resulting metal by a light deoxidizing agent andrecarburizing it to the desired extent by a recarburizing agent.

6. The method of producing high grade steel from lower grade materialand containing from about decimal three of one per cent. to one percent. and upward of carbon, consisting in melting and treating a chargeof the lower grade material by the open hearth method of treatment so aspartly to decarburize, desiliconize, demanganize, desulfurize anddephosphorize the metal and afterward subjecting the resulting moltenmetal to the electric furnace process; so as to produce molten metalpractically free from or low in carbon, silicon, sulfur, phosphorus andmanganese, deoxidizing the resulting molten metal by addition of a lightdeoxidizing agent and recarburizing it to the desired extent by arecarburizing agent.

7. The method of producing medium carbon steel, consisting indecarburizing, desiliconizin and demanganizing a molten charge of-ironto such an extent that it does not contain more than about decimal fourfive to decimal six of one per cent. of carbon and not more than aboutdecimal three of one per cent. of manganese and deoxidizing theresulting molten metal by addition thereto of a light deoxidizing agentas set forth. t

8. The method of producing medium carbon steel, consisting indecarburizing, desiliconizing and demanganizing a molten charge of ironto such an extent that it does not contain more than about decimal fourfive to decimal six of one per cent. of carbon and not more than aboutdecimal three of one per cent. of manganese, deoxidizing the resultingmolten metal by addition thereto of a light deoxidizing agent andrecarburizing the metal to the desired extent by addi tion thereto of arecarburizing agent.

. 9. The method of producing high grade steel from lower grade materialor stock and containing from about decimal three of one per cent. to oneper cent. and upward of carbon, consisting in decarburizing,desiliconizing and demanganizing a molten charge of the lower gradematerial and dephosphorizing and desulfurizing the partly purifiedcharge by the aid of the electric furnace process, deoxidizing theresulting molten'metal by addition thereto of a light deoxidizing agentand recarburizing it to the desired degree by a recarburizing agent.

10. The method of producing high grade steel from lower grade materialor stock and containing from about decimal three of one per cent. to oneper cent. and upward of carbon, consisting in decarburizing,desiliconizing and demanganizing a molten charge of the lower gradematerial by heat due to combustion and dephosphorizing and desulfurizingthe partly purified charge by the aid of heat produced by the aid of anelectric current, deoxidizing the resulting molten metal by the additionthereto of a light deoxidizing agent and recarburizing it to the desireddegree by addition thereto of a recarburizing agent.

11. The method of producing high grade high carbon steel, consisting indecarburiz-- ing, desiliconizing and demanganizing a molten charge ofiron, dephosphorizing and desulfurizing the partly purified charge bythe electric furnace process of treating iron, deoxidizing the resultingpurified metal by addition thereto of a light deoxidizing agent andrecarburizing it by addition thereto of a recarburizing agent so thatthe resulting metal contains about decimal eight of one per cent. andupward of carbon.

12. The method of producing high grade high carbon steel from lowergrade material,

'- consisting in treatinga molten charge of the lower grade material bythe electric furnace process so as to render the metal practically freefrom or very low in carbon, silicon, sulfur, phosphorus and manganese,deoxid izing the resulting metal by addition thereto of a lightdeoxidizing agent and recarburizing it by addition thereto of arecarburizing agent so as to produce steel containing from about decimaleight of one per cent. and upward of carbon, silicon Varying up to aboutdecimal three of one per cent. U

Signed at 22 Carlton House Terrace in the city of- Westminster Englandthis twelfth day of July 1917.

ROBERT ABBOTT HADFIELD. Witnesses:

WILLIAM Cnoss, LEONARD ROWLAND

